Various ways are recognized in the photographic industry for releasing a photographic inhibitor from a coupler in a photographic silver halide material and process. Release can be indirect through a linking or timing group or it can be direct, for example, upon reaction of the coupler with oxidized color developing agent during processing. Image-modifying couplers that release photographic inhibitors directly from the coupler are preferred in the photographic industry because manufacturing such couplers is easier, faster and less costly. However, many times direct release couplers, due to their inflexibility with regard to timing of release, are not practical for and effective at providing desired effects such as reduction of gradation, production of a finer color grain, improvement of sharpness through the so-called edge effect and improvement of color purity and color brilliance through inter-image effects. In this connection, reference is made to the article by C. R. Barr, J. R. Thirtle and P. W. Vittum entitled "Development-Inhibitor-Releasing (DIR) Couplers in Color Photography" in Photographic Science and Engineering 13, 74(1969).
The problem of timing of release has been addressed through the use of timing groups such as described in U.S. Pat. Nos. 4,248,962, 4,409,323 and 4,861,701. European Patent Applications 0 499 279 and 0 438 129 describe photographic compounds having a heterocyclic timing nucleus attached to a coupler moiety through an --O--C(O)-- or --OCH.sub.2 -- group, or other group capable of releasing the heterocyclic timing nucleus by electron transfer down an unconjugated chain. However, the use of timing groups can create other problems. For example, many couplers have little flexibility in their rate of release of a PUG, or in their synthetic design, as they are limited by the presence of a particular first timing or linking group, particularly with regard to substituents on such groups. More importantly, though, some couplers exhibit poor stability when stored for prolonged periods under tropical conditions. Thus, they are of limited practical value in today's photographic industry.
Triazoles have been described for use as development inhibitors and have been utilized in DIR couplers, see for example U.S. Pat. Nos. 5,200,306, 5,360,709, 5,306,607, 5,380,633 and 5,270,157. However, the particularly useful compounds of this invention have not been utilized or suggested.
Therefore, a need has existed for a photographic coupler that is synthetically simple to manufacture; has the flexibility to work in a variety of situations; and that is stable when stored for prolonged periods, especially under tropical conditions. The coupler should be capable of releasing a development inhibitor, thereby providing interlayer interimage effects and increased acutance for the image produced upon processing photographic material containing the coupler.